I am curious about live rock...
Does it truely require 2 wpg to run? I realize that if a coral or two comes w/ it, there will be a "die-back" period w/ the rock and that the rock needs to be cured, but besides the bacteria on live rock, what organisms inhabit it that are beneficial to the aquarium and do all of them require 2 wpg? If you only have 1 wpg, should you just purchase lace rock and let the cycle build up the bacteria colony in it?

I realize that not all live rocks are created equal... and that sometimes a bristle worm or mantis shrimp can sneak in w/ un-cured live rock... yikes!

Suppose a mantis shrimp does sneak in and is up to his usualy tom foolery... w/ all the live rock, I'd imagine he'd be tough to catch... what type of fish/invert/coral is he a threat too and who's a threat to him?

also, I've read that 1.022 is a minimum requirement for live rock, but fish can survive in 1.020-1.018 and that the lower content makes it easier to get oxygen in the water... true?

finally, a setup involving a cycled tank w/ standard rock... lace, coral molds, 1 inch of sand that is using a trickle filter and a good protien skimmer... will it be able to handle the needs of the tank, assuming proper concern is given to water changes, bio-load/stocking, etc..._________________20g planted - 1.5 wpg - pea gravel/sand/laterite - DIY co2

I will respond on the mantis; they are assassins and will kill anything that moves.
Just how dangerous depends on the size of the specimen; I have seen/captured them up to 12 inches here in Florida, and the commercial shrimpers call them "thumb splitters." Larger ones can and will crack the thin glass of a heater with no problem. You can catch them in the tank with a baited/modified soda bottle or a purchased trap designed for this purpose. They are really fascinating to watch and make for an excellent specimen display._________________Keepin' marines happy for 25 years

since starting the hobby I have learned one thing, bristleworms are my friend. I have never had any problems with them except accidental touching of them(fun with tweezers) they are a free little cleaning service. I personally remove large ones that I find but I have not seen any large bristleworms in my tank for quite some time and that is a good indicator that I am not overfeeding.

Personally I keep my salinity at 1.025 specific gravity. sometimes its 1.023 or even 1.026(at which time I add a bit of fw).

Skimmers are a must as far as I am concerened consider them a preventative messure for headaches! For the live rock I would say 2 watts per gallon also but 1 will be fine. this is because we want to give the attractive algae that grows on the live rock what it needs to live.

mantises are predators. though a lot of people keep them in small aquaria because of their intelligence. For a shrimp they're pretty smart. I have no idea about the oxygen bit if you have a skimmer your o2 levels should be fine. 1 inch of sand should be fine though I don't know about that trickle filter.